Moisture sensors are humidity-sensing capacitors. Various moisture sensors are known in the art including those found in U.S. Pat. Nos. 3,861,031, 5,075,667 and 5,027,077.
Typically moisture sensors have a porous alpha-Al2O3 film as a dielectric material with a conductive metal substrate as the bottom electrode and gold thin film as the top electrode. While conductive glues provide a simple and cost effective means for attaching a lead to an electrode it has not been possible to connect a lead to the top electrode using conductive glues in prior art sensor designs. More specifically, typical conductive glues and conductive pastes have to be avoided because they trap moisture when they are on the porous surface of the active sensing area. This trapped moisture significantly affects the sensors accuracy and response time for moisture levels of <−50° C. Dew Point.
Disclosed in this document is a new and improved moisture sensor having a structure that allows the lead to be connected to the top electrode with conductive glue or paste, which is away from the porous surface of the active sensing area and located on a dense insulating layer to improve the overall performance of the sensor.